Re: [PATCH v3 4/5] dma/pool: create dma atomic pool only if dma zone has managed pages

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On 12/13/21 6:27 AM, Baoquan He wrote:
Currently three dma atomic pools are initialized as long as the relevant
kernel codes are built in. While in kdump kernel of x86_64, this is not
right when trying to create atomic_pool_dma, because there's no managed
pages in DMA zone. In the case, DMA zone only has low 1M memory presented
and locked down by memblock allocator. So no pages are added into buddy
of DMA zone. Please check commit f1d4d47c5851 ("x86/setup: Always reserve
the first 1M of RAM").

Then in kdump kernel of x86_64, it always prints below failure message:

  DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
  swapper/0: page allocation failure: order:5, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-0.rc5.20210611git929d931f2b40.42.fc35.x86_64 #1
  Hardware name: Dell Inc. PowerEdge R910/0P658H, BIOS 2.12.0 06/04/2018
  Call Trace:
   dump_stack+0x7f/0xa1
   warn_alloc.cold+0x72/0xd6
   ? _raw_spin_unlock_irq+0x24/0x40
   ? __alloc_pages_direct_compact+0x90/0x1b0
   __alloc_pages_slowpath.constprop.0+0xf29/0xf50
   ? __cond_resched+0x16/0x50
   ? prepare_alloc_pages.constprop.0+0x19d/0x1b0
   __alloc_pages+0x24d/0x2c0
   ? __dma_atomic_pool_init+0x93/0x93
   alloc_page_interleave+0x13/0xb0
   atomic_pool_expand+0x118/0x210
   ? __dma_atomic_pool_init+0x93/0x93
   __dma_atomic_pool_init+0x45/0x93
   dma_atomic_pool_init+0xdb/0x176
   do_one_initcall+0x67/0x320
   ? rcu_read_lock_sched_held+0x3f/0x80
   kernel_init_freeable+0x290/0x2dc
   ? rest_init+0x24f/0x24f
   kernel_init+0xa/0x111
   ret_from_fork+0x22/0x30
  Mem-Info:
  ......
  DMA: failed to allocate 128 KiB GFP_KERNEL|GFP_DMA pool for atomic allocation
  DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA32 pool for atomic allocations

Here, let's check if DMA zone has managed pages, then create atomic_pool_dma
if yes. Otherwise just skip it.

Fixes: 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>



 Acked-by: John Donnelly <john.p.donnelly@xxxxxxxxxx>
 Tested-by:  John Donnelly <john.p.donnelly@xxxxxxxxxx>


Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
---
  kernel/dma/pool.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 5a85804b5beb..00df3edd6c5d 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -206,7 +206,7 @@ static int __init dma_atomic_pool_init(void)
  						    GFP_KERNEL);
  	if (!atomic_pool_kernel)
  		ret = -ENOMEM;
-	if (IS_ENABLED(CONFIG_ZONE_DMA)) {
+	if (has_managed_dma()) {
  		atomic_pool_dma = __dma_atomic_pool_init(atomic_pool_size,
  						GFP_KERNEL | GFP_DMA);
  		if (!atomic_pool_dma)
@@ -229,7 +229,7 @@ static inline struct gen_pool *dma_guess_pool(struct gen_pool *prev, gfp_t gfp)
  	if (prev == NULL) {
  		if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp & GFP_DMA32))
  			return atomic_pool_dma32;
-		if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp & GFP_DMA))
+		if (atomic_pool_dma && (gfp & GFP_DMA))
  			return atomic_pool_dma;
  		return atomic_pool_kernel;
  	}





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